T_APPL_DATA_LN_N1 subtest 3 fails on an LN-only server regardless of the response to a non-existing-object GET

I'm testing an embedded LN-only DLMS/COSEM server with the GXDLMSDirector Application Conformance Test. 13 of 14 tests pass; the only failing one is T_APPL_DATA_LN_N1, and it always fails on subtest 3 ("Read non-existing object").

The tool sends a GET for a non-existing object (class 15 / Association LN,
OBIS FF FF FF FF FF FF, attribute 1):

C0 01 C1 00 0F FF FF FF FF FF FF 01 00

The overall result is always:

T_APPL_DATA_LN_N1 subtest 3 succeeded when Short Name referencing is used.
T_APPL_DATA_LN_N1 failed.

To locate the expected behaviour I tried three different LN responses, and the verdict is identical in all three — the tool falls back to Short-Name referencing every time and marks the test failed:

Get-Response with data-access-result = object-undefined (4) → tool logs "Access Error: Device reports a undefined object". This is exactly what the Gurux reference server returns (GXDLMSLNCommandHandlers.GetRequestNormal → ErrorCode.UndefinedObject).
ExceptionResponse (D8 01 02) → no error message, but still falls back to SN.
A successful Get-Response returning the current Association LN object (logical name 0.0.40.0.0.255) → still falls back to SN.

Since none of these three responses is accepted for LN referencing, the verdict appears to be independent of the GET response itself.

Questions:

What does subtest 3 of T_APPL_DATA_LN_N1 expect an LN-only server to return for a non-existing-object GET, so that it passes without needing the Short-Name fallback?
Is this subtest expected to pass at all on an LN-only meter (one that returns an ExceptionResponse to SN reads)?

The server passes T_APPL_IDLE_N1, all T_APPL_OPEN_* tests, T_APPL_DATA_LN_N3/N4 and T_APPL_REL_P1, so basic LN GET/SET/ACTION and association handling are working. Thanks in advance.